While your device is connected, force restart it with these steps, but don't release the buttons when you see the Apple logo, wait until the connect to iTunes screen appears:

On an iPad Pro 11-inch or iPad Pro 12.9-inch: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Press and hold the Top button until your device begins to restart. Continue holding the Top button until your device goes into Recovery Mode.

On iPhone 8 and later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the connect to iTunes screen.

On an iPhone 7 or iPhone 7 Plus: Press and hold the Side and Volume Down buttons at the same time. Keep holding them until you see connect to iTunes screen.

On an iPhone 6s and earlier, iPad, or iPod touch: Press and hold both the Home and the Top (or Side) buttons at the same time. Keep holding them until you see the connect to iTunes screen.

When you see the option to Restore or Update, choose Update. iTunes will try to reinstall iOS without erasing your data. Wait while iTunes downloads the software for your device. If the download takes more than 15 minutes and your device exits the connect to iTunes screen, let the download finish, then repeat step 3.